WP admin bar disappearing as if public cache page is being served

Running OLS with Cyperpanel on Ubuntu 20.04. Wordpress websites with LSCache enabled.

The WP admin bar disappears on both of my websites after some time, as if the public cached page is getting served instead of the private cache page. This only started to happen today.

Any advice on how to debug this issue?
The issue goes away if I disable "Cache Logged-in Users", so it looks like my analysis is correct and OLS is grabbing the public cached page. Which seems like a bug.
From the documentation, OLS is supposed to support user-specific private caching. And sometimes I see page served with 'hit, private'. Also it was all working fine until today. I got confused with the '(LSWS v5.2.1+ required)' comment next to the 'Cache Logged-in Users' option
Taking back my comment above that it was all working fine until today. Early on I encountered an issue with the WP Zero Spam plugin where I was served a 403 error blocked page, which sounds exactly the same. I ended disabling the plugin, thinking that there lied the problem.

I also want to say that it's always possible that there is something odd with my config that's creating the problem. I'm reading LSCache is implemented through .htaccess so maybe something in my .htaccess file is interfering with proper functionality.
This just started happening again soon after I disabled Cloudflare proxying to try to see if HTTP/3 & QUIC were working with OLS 1.7.7 (which they are not).

David (who replied to my bug report email thread) says it's a usage issue, not a server bug. I don't really understand how this could a usage issue, maybe I am misunderstanding. A WP logged-in session should always be privately cached due to the _lscache_vary cookie. It would not make sense to me that a page from the public cache would be served in this case.